1. Field of the Invention
The present invention relates to a conveyor chain arrangement for a track maintenance machine, such as a ballast cleaning machine, comprising a machine frame, the conveyor chain arrangement being mounted on the machine frame for receiving and conveying ballast supporting a track defining a plane, and the conveyor chain arrangement comprising a vertically and transversely adjustable chain track extending longitudinally in an oblique plane with respect to the track plane adjacent a respective one of the machine frame sides, drive means connected to the chain track for vertically and transversely adjusting the chain track, an endless ballast excavating and conveying chain guided in the chain track, a chain drive for the chain, and the chain track including a ballast excavating beam extending in a horizontal plane underneath and substantially parallel to the track plane during operation and having an upper end providing a ballast discharge station spaced from the ballast excavating beam in the direction of a longitudinal extension of the machine frame and the lower chain track end forming a bent transition to the ballast excavating beam. The bent transition has an end leading and extending substantially parallel to the track plane.
2. Description of the Prior Art
U.S. Pat. No. 3,850,251 discloses such a conveyor arrangement on a track-bound ballast cleaning machine. While the machine is continuously moved on the track in an operating direction, the endless ballast excavating and conveying chain is guided along the ballast excavating beam underneath the track to excavate the ballast and the excavated ballast is conveyed upwardly along the chain track to a ballast cleaning screen arranged rearwardly of the ballast excavating beam in the operating direction and is there discharged for cleaning. The endless chain then moves downwardly along the opposite machine frame side back to the ballast excavating beam. A chain drive is arranged at the upper turning point of the chain, i.e. at the ballast discharge station. The bent lower ends of the two longitudinally extending chain track parts at the opposite sides of the machine frame are interconnected by the ballast excavating beam which consists of two parts linked to each other and to the lower chain track part ends. These ballast excavating beam parts may thus be pivoted into a V-formation to adjust the effective operating width of the ballast excavating beam. In this way, the conveyor arrangement may be used in tangent track as well as track switches where the ballast bed is much wider than in tangent track.
A similar ballast cleaning machine with a ballast excavating beam whose operating width may be adjusted has been disclosed in U.S. Pat. No. 4,614,238. In this conveyor arrangement, the two ballast excavating beam parts are either linked together or telescopingly connected, and a drive is provided for adjusting the length of the beam to the width of the ballast bed to be cleaned. When the length of the ballast excavating beam is adjusted, the length of the endless ballast excavating and conveying chain must be correspondingly changed to assure a proper guidance of the endless chain in the chain track.
U.S. Pat. No. 4,882,860 deals with a ballast excavating machine comprising an endless chain undercutter which is vertically adjustable at one side of the machine frame and may be pivoted about a vertical axis for operating beneath the track. The excavated ballast is upwardly conveyed and discharged onto a longitudinally extending conveyor for removing the excavated ballast. In its operating position, the undercutter cannot be vertically adjusted, which prevents adjustment of the excavating depth in accordance with changing operating conditions. The acute angle between the horizontally extending undercutter part beneath the track and the undercutter part rising to convey the excavated ballast to the removal conveyor makes the deflection of the endless chain from one to the other part difficult and subjects the chain to excessive wear. Also, this arrangement requires considerable space on the track shoulder, which substantially reduces the usefulness of the arrangement in track switches.
German patent application No. 2,226,612, published Jan. 4, 1973, discloses a ballast cleaning machine comprising two separate and independent ballast excavating units vertically adjustably arranged at respective sides of the machine frame and each having an endless excavating chain. The units are pivotal on the machine frame about horizontal axes extending transversely of the track. At the beginning of the operation, the ballast excavating units are pivoted into engagement with the ballast shoulders and are then turned about vertical axes into an operating position underneath the track. The excavated ballast is deposited along the shoulders alongside each machine frame side and must then be conveyed by bucket chains or conveyors to a ballast cleaning screen.
British patent No. 883,638 similarly discloses a ballast cleaning machine with two excavators comprising endless cutter chains mounted at the opposite sides of the machine frame for pivoting about vertical axes to extend underneath the track. The excavated ballast must be conveyed upwards from the track shoulders by elevators and is stored for removal on longitudinally extending conveyors. The structure is very complicated and inefficient in operation.